Phosphate esters of polyoxyalkylene ether block copolymers and their dispersants

ABSTRACT

A composition comprising a particulate solid and a dispersant which is a phosphate ester of a compound of formula 1: ##STR1## wherein Y is methoxy or H--(EO) q , m and q are each independently from 5 to 50 and n is from 5 to 70. When Y is a methoxy, n is preferably 20 and m is preferably 10. When Y is H--(EO) q , m and q are preferably 13 and n is preferably 30.

This application is the national phase of international application PCT/GB97/00930 filed Apr. 2, 1997.

The present invention relates to the use of phosphate esters of propylene oxide/ethylene oxide block co-polymers as dispersants for particulate solids in an organic medium and to compositions comprising such dispersants and particulate solids in an organic medium.

Phosphate esters of propylene oxide/ethylene oxide block copolymers (hereinafter PO/EO polymers) where the ester group is attached to EO are already known to the art. The known phosphate esters include both the alkyl end-capped PO/EO block copolymers and also EO/PO/EO block copolymers carrying phosphate ester groups at both ends of the polymer.

U.S. Pat. No. 4,613,445 discloses phosphate esters of end-capped block copolymers of formula AOPOEO wherein A is inter alia C₁₋₂₄ -alkyl and their use as corrosion inhibitors. This patent also discloses compositions comprising the phosphate esters, a buffer and an alcohol.

CA 2027302 discloses aqueous coolant compositions containing phosphate esters derived from fatty alcohol PO/EO polymers and EO/PO/EO block copolymers.

U.S. Pat. No. 3,658,959 discloses carbamate insecticidal compositions containing phosphate esters of EO/PO/EO block copolymers and aqueous solutions or dispersions derived therefrom.

DE 3542441 discloses bis-monophosphate esters of EO/PO/EO block copolymers and their use in the manufacture of plant protection formulations which are essentially solvent-free.

These publications disclose either aqueous compositions containing the phosphate esters of PO/EO copolymers or concentrates for use in aqueous systems and none envisage the use of such esters to disperse particulate solids, especially pigments, in non-aqueous media.

It has now been found that phosphate esters of PO/EO block copolymers wherein the phosphate ester is attached to EO are useful for dispersing particulate solids in organic liquids and especially in the preparation of mill bases for use in paints and printing inks.

According to a first aspect of the invention there is provided a composition of a particulate solid and a dispersant which is a phosphate ester of a compound of formula 1: ##STR2## including salts thereof. wherein

Y is a group RO-- or a group H--(EO)_(q) ;

R is C₁₋₆ -alkyl;

m and q are each, independently, from 5 to 50; and

n is from 5 to 70.

In a second aspect of the invention there is provided a composition comprising a dispersion of a particulate solid in an organic medium containing a dispersant which is a phosphate ester of a compound of formula 1.

In a third aspect of the invention there is provided a non-aqueous mill-base comprising a particulate solid, a film-forming resin, an organic medium and a dispersant which is a phosphate ester of a compound of formula 1.

In a fourth aspect of the invention there is provided the use of a phosphate ester of a compound of formula 1 to disperse a particulate solid in an organic medium, especially a mill base.

The organic medium is preferably an organic liquid containing not greater than 50%, more preferably not greater than 20% and especially not greater than 10% by weight water. It is especially preferred that the organic medium is substantially free from water.

When Y is the group RO--, the dispersant is a phosphate ester of an end-capped PO/EO block copolymer which preferably contains either 1 or 2 groups of formula RO(PO)_(n) (EO)_(m) -- attached to each phosphorus atom and especially mixtures thereof.

When Y is in the group H--(EO)_(q) the compound of formula 1 is a diol and the dispersant is a phosphate ester which preferably contains a phosphate group at each end of the diol. It is also preferred that each phosphorus atom forms an ester linkage with either 1 or 2 diols of formula H--(EO)_(q) (PO)_(n) (EO)_(m) --H and it is especially preferred that the dispersant is a mixture of such esters.

R may be linear or branched but is preferably linear and is especially methyl.

When Y is the group RO--, n and m are preferably and independently from 5 to 40 and especially from 5 to 25. It is also preferred that the ratio of m to n is from 3:1 to 1:3 and especially from 2:1 to 1:2.

The MW of the end-capped block copolymer of formula RO(PO)_(n) (EO)_(m) --H from which the dispersant is derived is preferably not less than 500 and more preferably not less than 1000. It is also preferred that the MW of this end-capped copolymer is not greater than 3,000 and especially not greater than 2,000.

When Y is the group H--(EO)_(q) --, m and q are preferably the same and are preferably, independently, from 5 to 20. In the case of the diol of formula H--(EO)_(q) (PO)_(n) (EO)_(m) --H it is also preferred that the ratio of (q+m) to n is from 1:1 to 1:5 and especially from 1:1 to 1:3. The MW of the diol of formula H--(EO)_(q) (PO)_(n) (EO)_(m) --H from which the dispersant is derived is preferably less than 5,000 and especially less than 4,000.

The particulate solid can be any material which it is desired to stabilise in a finely divided state in the organic medium. Examples of suitable solids are pigments and fillers for inks, paints and other surface coatings; magnetic metals or alloys and magnetic oxides, for use in the production of magnetic tapes, discs and memory devices; dirt and soil particles; biocides, agrochemicals and pharmaceuticals. The composition, whether dry or in the form of a dispersion, may contain other ingredients such as resins, binders, fluidising agents, anti-sedimentation agents, plasticisers, humectants, coalescents, co-solvents, thickeners and preservations. These ingredients may be soluble in, partially soluble in, insoluble in, or dispersed in the organic medium.

If the solid is a pigment, it may be organic or inorganic. Preferably the solid is an inorganic pigment, a metallic pigment, or a metal salt of an organic dyestuff (sometimes referred to as a lake or toner). It may come from any of the recognised classes of pigments described, for example, in the Third Edition of the Colours Index (1971) and subsequent revisions and supplements thereto, under the chapter headed "Pigments".

Examples of organic pigments are those from the azo, disazo, condensed azo, thioindigo, indanthrone, isoindanthrone, anthanthrone, anthraquinone, isodibenzanthrone, triphendioxazine, quinacridone and phthalocyanine series, especially copper phthalocyanine and its nuclear halogenated derivatives and also lakes of acid, basic and mordant dyes.

Examples of inorganic pigments are titanium dioxide (including Anatase and Rutile forms, and high UV absorbing ultra-fine titanium dioxide), zinc oxide, Prussian Blue, cadmium sulphide, iron oxides (including transparent iron oxides), ultramarine, mica (including pearlescent pigments made by surface treating mica with, for example fine titanium dioxide) and the chrome pigments, including chromates, molybdates, and mixed chromates and sulphates of lead, zinc, barium, calcium and mixtures and modifications thereof which are commercially available as greenish-yellow to red pigments under the names of primrose, lemon, middle, orange, scarlet and red chromes.

It is to be understood that the term inorganic pigment also includes carbon black, especially the chemically modified or coated versions of carbon black used in the printing and paint industries.

Examples of metallic pigments are aluminium flake, copper powder and copper flake.

Examples of metal salts of organic dyestuffs are the azo metal salt pigments such as Cl Pigment Red 48 (also known as 2B Toner or Permanent Red 2B), Cl Pigment Red 53 (also known as Lake Red C or Red Lake C), Cl Pigment Red 52, Cl Pigment Red 57 (also known as 4B Toner, Lithol Rubine, Rubine Toner or Permanent Red 4B), Cl Pigment Red 58, Cl Pigment Red 247, Cl Pigment Yellow 61, Cl Pigment Yellow 62, Cl Pigment Yellow 183 and Cl Pigment Yellow 191.

Examples of fillers are calcium carbonate, hydrated alumina, talc, quartz, silica (precipitated, pyrogenic and synthetic), metal silicates, barium and calcium sulphate, china clay, antimony oxide, powdered slate, wollastonite and chopped glass fibre.

Preferably the particulate solid is a pigment, particularly an inorganic pigment and especially titanium dioxide.

The organic medium may be a film-forming resin, but is preferably a liquid which is either a polar or non-polar organic liquid. The choice of organic liquid depends to a large extent on the end-use to which the dispersion is to be put. Thus, when the dispersion is to be used in a printing or packaging ink or mill-base therefor, the organic liquid is preferably a polar organic liquid. When the dispersion is to be used in a solvent-based paint or aqueous emulsion paint or mill-base therefor, the organic liquid is preferably non-polar.

The term polar organic liquid are those liquids capable of forming moderate or strong hydrogen bonds as described in the article entitled "A three dimensional approach to solubility" by Crowley et al in Journal of Paint Technology, Volume 38, 1966 at page 269. Such organic liquids have a hydrogen bonding number of 5 or more as defined in this article.

Examples of polar organic liquids are amines, ethers, especially C₁₋₆ -alkyl ethers, organic acids, esters, ketones, glycols, alcohols and amides including mixtures thereof. Numerous specific examples of such moderately and strongly hydrogen bonding liquids are given in the book entitled "Compatibility and Solubility" by Ibert Mellan (published 1968 by Noyer Development Corporation) in Table 2.14 on pages 28 and 40 and these organic liquids all fall within the scope of polar organic liquids as used in the present description.

Preferred polar organic liquids are dialkylketones, alkylesters of alkanecarboxylic acids, alkanols especially C₁₋₆ -alkanols. Examples of preferred and especially preferred polar organic liquids are dialkylketones such as acetone, methylethylketone (MEK), diethylketone, diisopropylketone, methylisobutylketone and diisobutylketone; alkylesters such as methylacetate, ethylacetate, isopropylacetate, ethylformate, methylpropionate and ethylbutyrate; alkoxyalkylesters such as methoxypropylacetate and alkanols such as methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol.

When the dispersion or mill-base is used to prepare a printing or packaging ink, the polar organic liquid is preferably ethanol or ethyl acetate, especially mixtures thereof, or methoxypropylacetate.

The term non-polar liquid are those liquids which are immiscible with water and include aliphatic and aromatic hydrocarbons and their halogenated analogues. Examples are pentane, hexane, heptane, octane, benzene, toluene, xylene, paraffin and petroleum fractions and distillates such as white spirits.

When the dispersion or mill-base is used in the preparation of a solvent-based paint, the non-polar solvent is preferably white spirits.

The dispersion may be made by any method known to the art. Thus, it may be made by mixing together the dispersant, particulate solid and organic liquid and grinding or milling the mixture to obtain a stable dispersion of the particulate solid in the organic liquid. Preferably, the particulate solid is ground or milled until the mean particle size is less than 15μ diameter, more preferably less than 10μ and especially less than 3μ.

The amount of dispersant is preferably at least 0.2%, more preferably at least 0.5% and especially at least 1% by weight based on the weight of particulate solid. Preferably, the amount of dispersant is not greater than 100%, preferably not greater than 50%, more preferably not greater than 20% and especially not greater than 10% by weight based on the weight of particulate solid.

A dry composition consisting essentially of the particulate solid and dispersant may be prepared by removing the organic liquid from the above mentioned dispersion. In such a case the organic liquid is preferably volatile to facilitate its removal. The dry composition so obtained consists essentially of the finely divided particulate solid which contains a surface coating of the dispersant. Such dry composition can be added to an organic medium to provide a uniform distribution of the particulate solid throughout the medium.

As noted hereinbefore, the dispersant may be used to prepare a mill-base comprising the particulate solid, dispersant, organic liquid and a film-forming resin. Implicit in the definition of mill-base is the grinding or milling of the particulate solid in the presence of both the dispersant and the film-forming resin.

The film-forming resin may be any resin known to the art, especially those used in the preparation of printing and packing inks and coatings especially flexographic inks and also resins used in the preparation of solvent-based paints.

Examples of film-forming resins which are used in the preparation of printing and packaging inks are nitrocellulose resins and resins obtainable by polymerising ethylenically unsaturated carboxylic acid esters such as polyvinylbutyrate.

The film-forming resins used in the preparation of solvent-based paints include both natural and synthetic resins such as alkyd resins, alkyd/melamine formaldehyde resins, air-drying alkyd resins, long oil alkyd resins and urethane long oil resins.

The dispersion or mill-base according to the invention preferably contains at least 5%, more preferably at least 20% and especially at least 40% by weight particulate solid based on the total weight of the dispersion or mill-base. Preferably the dispersion or mill-base contains not greater than 90%, more preferably not greater than 80% and especially not greater than 70% by weight particulate solid based on total weight of the dispersion or mill-base.

The mill-base according to the invention preferably contains greater than 2%, more preferably greater than 5% and especially greater than 10% by weight of film-forming resin based on the total weight of mill-base. It is preferred that the amount of film-forming resin is not greater than 40%, preferably not greater than 30% and especially not greater than 20% based on the total weight of the mill-base.

The mill-bases are generally diluted or let-down with a mixture of film-forming resin and organic liquid to give the final printing or packaging ink formulation or paint formulation. This final formulation may contain other adjuvants commonly added to inks or paints and such adjuvants are preferably added to the let-down. Examples of such adjuvants are extenders and materials which improve the flow characteristics of the ink or paint during application such as esters of aliphatic acids. Examples of such esters are di-octylphthalate, diisohexylphthalate, didecylphthalate, di-undecylphthalate, di(2-ethylhexyl)phthalate and di-octyladipate.

As disclosed hereinbefore there is provided the use of a phosphate ester of a compound of formula 1 to disperse a particulate solid in a non-aqueous mill-base. Whereas it is preferred that the phosphate ester is the prime dispersant for dispersing the particulate solid in the organic liquid of the mill base, the phosphate ester of the compound of formula 1 may also be used as a secondary dispersant for addition to a mill base or formulated ink or paint to improve the properties thereof.

The inks and paints made from the aforementioned dispersion or mill base exhibit enhanced properties compared with dispersions and mill bases prepared using alternative dispersants, especially enhanced gloss, transparency, brightness and reduced haze.

As disclosed hereinbefore the phosphate esters of the compound of formula 1 are already known in the art and are typically prepared by heating a compound of formula 1 in an inert atmosphere with a phosphating agent such as phosphoric acid, polyphosphoric acid or phosphorus pentoxide at a temperature between 70 and 150° C. The dispersants are obtained as pourable liquids or low melting gums and waxes.

The reaction between the phosphating agent and the compound of formula 1 may optionally be carried out in the presence of an alcohol or alkanolamine or the phosphate esters of the compound of formula 1 may be subsequently heated with an alcohol or alkanolamine. When the reaction involves an alcohol the phosphate end group(s) are further partially esterified. When the reaction involves an alkanolamine additional ester and/or amide groups and/or amine salts of the phosphate ester of the compound of formula 1 are formed. It is believed that the reaction product is mainly an amine salt.

The phosphate ester of the compound of formula 1 may also be present as the salt of an alkali metal or ammonia.

The following phosphate esters have been evaluated as dispersants for particulate solids in the organic medium and the references to the various agents in the tables below are retained throughout the following examples:

                  TABLE A                                                          ______________________________________                                         A) Dispersants which are phosphate esters of a copolymer of                      general formula MeO(PO).sub.n (EO).sub.m -H. They were prepared               by reacting the end-capped PO/EO polymer with P.sub.2 O.sub.5.                                       Polymer to                                                                               n m P                                                                         .sub.2 O.sub.5 ratio Appearance                ______________________________________                                         Dispersant 1                                                                            10     20     2:1      Brown waxy solid                                 Dispersant 2 15 15 2:1 Brown viscous liquid                                    Dispersant 3 20 10 2:1 Brown viscous liquid                                    Dispersant 4 10 20 3:1 Brown waxy solid                                        Dispersant 5 15 15 3:1 Brown viscous liquid                                    Dispersant 6 20 10 3:1 Brown viscous liquid                                  ______________________________________                                    

                  TABLE B                                                          ______________________________________                                         B) Dispersants which are phosphate esters of a copolymer of                      general formula H-(EO).sub.q (PO).sub.m (EO).sub.n -H. They were              prepared by reacting the EO/PO/EO block copolymer with P.sub.2 O.sub.5.                                   Polymer to                                                                               q n m P                                                                       .sub.2 O.sub.2 ratio Appearance           ______________________________________                                         Dispersant 7                                                                            9.7    16.4   9.7  3:1      Yellow oil                                  Dispersant 8 13.1 30.2 13.1 3:1 Yellow oil                                     Dispersant 9 6.25 56.0 6.25 3:1 Pale brown oil                                 Dispersant 10 7.95 47.4 7.95 3:1 Brown liquid                                  Dispersant 11 9.09 56.0 9.09 3:1 Brown liquid                                  Dispersant 12 12.95 35.3 12.95 3:1 Yellow oil                                ______________________________________                                          Footnote to Table B                                                            The EO/PO/EO block copolymers used to make Dispersants 712 were Synperoni      PE/L35, Synperonic PE/L64, Pluronic L101, Synperonic PE/L92, Pluronic P10      and Pluronic L72 respectively.                                           

The invention is further illustrated with reference to the following examples wherein all amounts are given in parts by weight unless indicated to the contrary.

EXAMPLES 1-4 Mill Bases for Nitrocellulose Flexographic Inks Containing Permanent Yellow PGRL04

A mill-base was prepared by milling a mixture of Permanent Yellow PGRL04 (30 parts ex Hoechst), dispersant (4.35 parts) and nitrocellulose resin (65.65 parts as a 16% w/w solution in a mixture of ethanol/ethylacetate (3:1), SM 1359 ex Coates Lorilleux) in the presence of 3 mm glass beads (125 parts) for 30 minutes. The mill base was then separated from the glass beads and let down with a mixture of SM 1359 (131.05 parts), dioctylphthalate (11.42 parts) and ethanol/ethylacetate (5:1, 57.53 parts) to give a printing ink containing 10% w/w pigment. The ink was allowed to de-aerate and then applied to paper using a K-proofer (ex. Sheen Instruments) to give a film thickness of 1.2μ. The film was air-dried for 90 minutes and then cured by heating at 120° C. for 20 minutes. The 60° gloss angle of the film was then measured using a Novogloss meter (Rhopoint Instrumentation, UK).

The results are given in Table 1 below and show that the inks of the present invention exhibit superior gloss compared with a conventional agent derived from an EO/PO block copolymer derived from diethylaminoethanol.

                  TABLE 1                                                          ______________________________________                                         Example        Dispersant                                                                              60° gloss                                       ______________________________________                                         1              7        25.6                                                     2 8 28.5                                                                       3 9 19.9                                                                       4 10 22.5                                                                      Control S 21.3                                                               ______________________________________                                          Footnote to Table 1                                                            Dispersant S is Agent J of US 4,518,435.                                 

EXAMPLES 5-8 Mill Bases for Flexographic Inks Containing Special Black 4

These mill bases were prepared by the manner described in Examples 1-4 except using Special Black 4 (25 parts, ex Degussa), dispersant (5.42 parts) and nitrocellulose resin (SM 1359; 68.22 parts 16% w/w solution in a mixture of ethanol/ethylacetate (3:1)) in place of the Permanent Yellow, dispersant and resin for preparing the mill bases of Examples 1-4.

These mill bases were let down with nitrocellulose resin (SM 1359; 101.93 parts) dioctylphallate (8.9 parts) and ethanol/ethylacetate (5:1, 39.7 parts) in place of the let down formulation of Examples 1-4. The resulting printing inks containing 10% pigment were evaluated as described in Examples 1-4 and the results given in Table 2 below. These results show that inks made according to the present invention exhibit superior gloss compared with inks prepared using a conventional dispersant derived from an EO/PO block copolymer.

                  TABLE 2                                                          ______________________________________                                         Example        Dispersant                                                                              60° C. gloss                                    ______________________________________                                         5              7        18.1                                                     6 8 17.9                                                                       7 9 17.0                                                                       8 10 18.3                                                                      Control S 11.3                                                               ______________________________________                                          Footnote to Table 2                                                            Dispersant S is as described in the footnote to Table 1.                 

EXAMPLE 9 Use of Dispersant 6 as Secondary Dispersing Agent in Long Oil Alkyd Paint

Titanium dioxide (35 parts, Tioxide TR92) and a long-oil alkyd resin (18.8 parts as 20% (w/w) resin in white spirits, Synolac 50W ex Cray Valley) were milled together with 3 mm glass beads (125 parts) for 15 minutes in a Red Devil shaker. The paint was then let down by adding more resin in white spirits (50 parts of 75% (w/w) Synolac 50W in white spirits). This paint was decanted from the beads and let down further with a mixture of long-oil alkyd resin (3.3 parts of 75% (w/w) Synolac 50W in white spirits), white spirits (5.1 parts) and mixed calcium/cobalt/zirconium driers (4.4 parts).

The final paint was divided into three portions and Dispersant 6 and Dispersant S, respectively, were added to separate portions in an amount of 5% (w/w) dispersant based on weight of paint. These paint samples were applied to paper using a K-proofer as described in Examples 1-4 and the paint-films dried and cured as previously described. The gloss/haze of the paint-film was measured using a Byk Garner glossmeter and the LAB colour co-ordinates were measured using a Dr. Lange Colorimeter. The results are given in Table 3 below and show that the paint containing Dispersant 6 as secondary dispersing agent exhibits superior gloss and reduced haze compared with the control and Dispersant S and that Dispersant 6 gives a paint of superior whiteness and blueness of shade.

                  TABLE 3                                                          ______________________________________                                         Dispersing                                                                             Gloss                                                                  Agent   20°                                                                            60°                                                                              Haze  L      A    B                                    ______________________________________                                         Dispersant 6                                                                           86.4   94.1     28.6  96.3   -0.3 2.4                                    Dispersant S 80.0 91.7 48.1 95.9 0 3.4                                         Control 82.0 90.9 36.0 95.8 -0.3 3.1                                         ______________________________________                                          Footnote to Table 3                                                            Control contains no secondary dispersant.                                      Dispersant S is as described in the footnote to Table 1.                 

EXAMPLE 10 Use of Dispersant 6 as Primary Dispersing Agent in White Spirit Paint

A white millbase was prepared by milling together titanium dioxide and a long-oil alkyd resin in white spirits both in the presence and absence of Dispersant 6. The amounts of the various components are listed in Table 4A below

                  TABLE 4A                                                         ______________________________________                                         Example or Comparative Example                                                                      10     Control                                            ______________________________________                                         Tioxide TR 92        35.35  35                                                   Dispersant 6 2.14 --                                                           Synolac 50W 4.88 18.8                                                          (75% in white spirits)                                                         White Spirits 12.0 5.1                                                       ______________________________________                                    

The millbases were prepared by milling the titanium dioxide and resin with and without Dispersant 6 for 15 minutes on a Red Devil shaker in the presence of 3 mm glass beads (125 parts). The millbase was then separated and let down with a mixture of 75% Synolac 50W in white spirits (3.3 parts), white spirits (5.1 parts) and mixed driers (4.4 parts) as described in Example 9. The resultant paint was then applied to card, dried and cured as described in Example 9 and the gloss, haze and colour co-ordinates determined as in the previous example. The results are given in Table 4b below which show that millbase containing Dispersant 6 exhibits superior gloss and significantly reduced haze compared with the control wherein the resin is the sole dispersing agent.

                  TABLE 4B                                                         ______________________________________                                         Gloss                                                                          20° 60°                                                                              Haze    L      A    B                                      ______________________________________                                         Example 10                                                                             86.8   92.4     16.0  96.1   -0.6 1.0                                    Control 76.9 84.9 29.2 96.0 -0.8 1.0                                         ______________________________________                                    

EXAMPLE 11 Use of Dispersant 6 as Primary Dispersant in Polyester Paint

A white millbase was prepared by milling together the various components in the amounts given in Table 5a below using the method described in Example 10.

                  TABLE 5A                                                         ______________________________________                                         Example          11     Control                                                ______________________________________                                         Tioxide TR 92    54.74  39.6                                                     Dispersant 6 3.32 --                                                           Aroplaz 6820 3.43 4.26                                                         Butanol 0.52 3.41                                                              MPA 10.98 13.65                                                              ______________________________________                                          Footnote to Table 5a                                                           Aroplaz 6820 is a polyester/melamine formaldehyde resin supplied by            Rheichold, USA.                                                                MPA is methoxypropylacetate.                                             

The millbase was then separated from the glass beads and let down with the formulations in the amounts given in Table 5b below.

                  TABLE 5B                                                         ______________________________________                                         Example          11     Control                                                ______________________________________                                         Aroplaz 6820     44.47  30.38                                                    Cymel 303 20.74 15.0                                                           Butanol 13.76 8.67                                                             MPA 16.71 27.12                                                                Butylacetate 16.71 12.23                                                       Xylene 5.57 4.08                                                             ______________________________________                                          Footnote to Table 5b                                                           Cymel 303 is a melamine/formaldehyde crosslinking resin ex American            Cyanamid.                                                                

The resulting paint formulation was sprayed onto card and then dried and cured as described in Example 9. The gloss, haze and colour co-ordinates were measured as described in Example 9 and the details given in Table 5c below. These data show that the gloss is significantly higher in the case of the paint prepared from the millbase containing Dispersant 6 compared with the paint prepared from the millbase where the resin acts as dispersing agent. The haze of the paint containing Dispersant 6 is also much lower.

                  TABLE 5C                                                         ______________________________________                                         Gloss                                                                          20° 60°                                                                              Haze    L      A    B                                      ______________________________________                                         Example 11                                                                             96.6   103.6    40.4  98.6   -0.3 0.7                                    Control 86.5 96.5 53.8 98.4 -0.4 0.5                                         ______________________________________                                    

EXAMPLES 12 to 18 Use of Dispersants in Alkyd Resin/white Spirits Paint

A white millbase was prepared by milling titanium dioxide (60 parts; Kronos 2190), dispersant (2.4 parts), resin (30.76 parts; Wresinol AF 9300 (100%) ex. Resinous Chemicals Ltd) and white spirits (6.84 parts) for 20 minutes in a 4 oz bottle containing 3 mm glass beads (125 parts) using a Red Devil shaker. The millbase contained 77% (w/w) resin based on weight of millbase.

A control was also prepared wherein the dispersant was replaced by an equal weight of white spirits.

The beads were then removed from the millbase which was added to a letdown formulation to form the final paint. The letdown contained Wresinol AF 9300 (45.98 parts), white spirits (12.52 parts), methylethylketoxime (0.61 parts) and mixed driers (6.29 parts, Durham VX71 ex. Durham Chemicals).

The paint was then applied to a non-glossy card using K-bar number 4 (36μ wet film thickness) dried and cured as described in Examples 1-4. The gloss/haze of the paint-film was measured using a Byk Garner glossmeter and the LAB co-ordinates were measured using a Dr. Lange Colormeter. The results are given in Table 6 below:-

                  TABLE 6                                                          ______________________________________                                                   Gloss                                                                Example                                                                               Dispersant                                                                              20°                                                                            60°                                                                           Haze L     a    b                                 ______________________________________                                         12     6        93.1   102   34.2 98.9  -0.8 -0.2                                13 11 81.6 91.5 31.9 99.5 -0.6 0.7                                             14 12 80.6 91.2 43.9 99.3 -0.5 0.1                                             15 10 80.5 92.4 78.3 98.2 -0.4 -0.1                                            16 9 79.5 89.9 87.6 98.3 -0.5 -0.2                                             17 8 70.9 87.6 159 98.4 -0.3 0.4                                               18 7 59.6 85.7 173 97.9 -0.9 0.7                                                S 72.4 90.8 107 98.0 -0.3 0.4                                                 Control -- 73.6 85.6 42.2 98.5 -0.6 0.1                                      ______________________________________                                          Footnote to Table 6                                                            Dispersant S is as described in the footnote to Table 1.                 

EXAMPLES 19 to 25

Examples 12 to 18 were repeated with a yellow reduced shade tinter wherein the white paint (5 parts) was stirred with a yellow tinter (0.56 parts). The yellow tinter was prepared by milling together Hostaperm Yellow H3G (37.5 parts, Ex. Hoechst), dispersant (4.5 parts), fluidising agent (1.12 parts) and water (56.88 parts) for 30 minutes in a 4 oz bottle in the presence of glass beads (3 mm diameter, 125 parts) using a Red Devil shaker. The beads were then separated, and the yellow dispersion let down with propylene glycol (56.88 parts) to give the yellow tinter. The results are given in Table 7 below.

                  TABLE 7                                                          ______________________________________                                         Ex-            Gloss                                                           ample Dispersant                                                                              20°                                                                            60°                                                                          L    a    b    % Strength                           ______________________________________                                         19    6        56.1   88.3 94.5 -2.5 27.2 2.3% stronger                          20 9 55.9 87.1 94.2 -3.6 31.0 4.7% stronger                                    21 12 51.2 84.2 94.0 -2.8 26.2   6% stronger                                   22 11 43.8 86.6 93.1 -3.2 32.8  15% stronger                                   23 8 40.0 82.7 93.0 -3.7 34.6  15% stronger                                    24 7 28.2 70.3 92.4 -3.2 32.4  21% stronger                                    25 10 3.4 20.6 89.6 -3.0 36.5  53% stronger                                     S 40.8 81.9 95.1 -0.1 18.6 2.2% weaker                                        Control -- 37.7 78.3 94.8 -0.9 21.4 --                                       ______________________________________                                          Footnote to Table 7                                                            Dispersant S is as described in the footnote to Table 1                  

EXAMPLES 26 to 30

Examples 12 to 18 were repeated with a red iron oxide tinter (0.56 parts ex. Hollidays) mixed with the white base paint. The results are given in Table 8 below.

                  TABLE 8                                                          ______________________________________                                         Ex-            Gloss                                                           ample Dispersant                                                                              20°                                                                            60°                                                                          L    a    b    % Strength                           ______________________________________                                         26    6        61.8   84.6 54.6 21.7 5.1  22.4% stronger                         27 8 35.1 74.9 49.7 23.7 7.6 98.5% stronger                                    28 9 50.1 81.3 53.1 22.2 6.3   43% stronger                                    29 12 63.9 84.9 54.8 20.7 4.2   16% stronger                                   30 11 18.8 67.9 49.0 23.9 7.6  110% stronger                                   Control --  65.4 84.9 56.8 20.8 4.5 --                                       ______________________________________                                    

EXAMPLES 31 to 35

Examples 26 to 30 were repeated except that the red iron oxide tinter was replaced by the same weight of violet tinter ex. Huls GmbH. The results are given in Table 9 below.

                  TABLE 9                                                          ______________________________________                                         Ex-            Gloss                                                           ample Dispersant                                                                              20°                                                                            60°                                                                          L    a    b    % Strength                           ______________________________________                                         31    6        39.3   78.1 68.9 8.2  -23.3                                                                                1.7% stronger                         32 8 14.5 59.4 57.5 15 -33.6  150% stronger                                    33 9 55.4 82.9 65.6 10.3 -26.4   32% stronger                                  34 12 49.4 81.2 66.6 9.4 -24.4   22% stronger                                  35 11 26.2 70.1 57.9 13.5 -32  143% stronger                                   Control --  51.2 84.1 69.1 7.9 -20.8 --                                      ______________________________________                                     

What is claimed is:
 1. A composition comprising a dispersion of a pigment in an organic medium containing a dispersant which is a phosphate ester of a compound of Formula 1 ##STR3## including salts thereof whereinY is H--(EO)--_(q) ; PO and EO represent propyleneoxy and ethyleneoxy, respectively; m and q are each, independently, from 5 to 50; and n is from 5 to
 70. 2. A composition as claimed in claim 1 wherein m and q are each, independently, from 5 to
 20. 3. A composition as claimed in claim 1 wherein the ratio of (q+m) to n is from 1:1 to 1:5.
 4. A composition as claimed in claim 1 wherein the pigment is titanium dioxide.
 5. A composition as claimed in claim 1 wherein the organic medium is an organic liquid containing not greater than 10% by weight water.
 6. A composition as claimed in claim 1 wherein the organic medium is white spirits.
 7. A composition as claimed in claim 1 wherein the organic medium is a polar organic liquid.
 8. A composition as claimed in claim 7 wherein the polar organic liquid is an alcohol or a glycol.
 9. A non-aqueous millbase comprising a pigment, a film-forming resin, an organic medium and a dispersant which is a phosphate ester of a compound of Formula 1 ##STR4## including salts thereof whereinY is a group RO-- or a group H--(EO)--_(q) ; PO and EO represent propyleneoxy and ethyleneoxy, respectively; R is C₁₋₆ -alkyl; m and q are each, independently, from 5 to 50; and n is from 5 to
 70. 10. A non-aqueous millbase as claimed in claim 9 wherein R is methyl.
 11. A non-aqueous millbase as claimed in claim 9 wherein m and n are each, independently, from 5 to 25 when Y is the group RO--.
 12. A non-aqueous millbase as claimed in claim 9 wherein the ratio of m to n is from 2:1 to 1:2 when Y is the group RO--.
 13. A non-aqueous millbase as claimed in claim 9 wherein m and q are each, independently, from 5 to 20 when Y is the group H--(EO)_(q) --.
 14. A non-aqueous millbase as claimed in claim 9 or claim 13 wherein the ratio of (q+m) to n is from 1:1 to 1:5 when Y is the group H--(EO)_(q) --.
 15. A non-aqueous millbase as claimed in claim 9 wherein the pigment is titanium dioxide.
 16. A paint or printing ink comprising a pigment, film-forming resin, an organic medium and a dispersant which is a phosphate ester of a compound of Formula 1 ##STR5## including salts thereof whereinY is a group RO-- or a group H--(EO)_(q) --; PO and EO represent propyleneoxy and ethyleneoxy, respectively; R is C₁₋₆ -alkyl; m and q are each, independently, from 5 to 50; and n is from 5 to
 70. 17. A paint or printing ink as claimed in claim 16 which contains water.
 18. A paint or printing ink as claimed in claim 17 wherein the amount of water is not greater than 10% by weight of the organic medium.
 19. A paint or printing ink as claimed in claim 16 wherein the pigment is titanium dioxide. 